Field of the Invention
The present invention relates to a technique for correcting an image shake in an optical apparatus, an image pickup apparatus or the like.
Description of the Related Art
An image shake can be caused on an image captured by an image pickup apparatus such as a digital camera by a shaking of a user's hand which holds a camera main body when capturing the image. Therefore, there have been some apparatuses with a function for detecting vibration applied to the camera main body to correct the image shake of an object image. In this technique, optical image shake correction processing and electronic image shake correction processing are known. The optical image shake correction processing detects a shake of a camera main body with an angular velocity sensor or the like to move an optical member in a photographing optical system (a correcting lens) to change a direction of an optical axis in the photographing optical system. Thereby, the image focused in a light receiving plane of an imaging element can be moved to correct the shake. Also, the electronic image shake correction processing is processing for artificially correcting the image shake by performing image processing on a captured image.
A shake detection signal output from the angular velocity sensor or the like comprises a signal caused by the vibration such as a hand shaking that should be corrected. In addition, the shake detection signal comprises a signal or the like caused by an operation of a camera according to a photographer's intension, such as a panning operation. Thereby, when the correcting lens is driven based on only the shake detection signal, an image shake correction is performed on a large shake, for example, during a panning or a tilting operation (hereinafter referred to as a “panning operation or the like”). Therefore, a target position of the correcting lens may be greater than a movable range thereof. Alternatively, an image-swing (swing-back) can occur after the panning operation or the like to cause the user to feel discomfort about the operation of the camera or the image. A Processing for the correcting the swing-back stops the image shake correction if the shake detection signal of the angular velocity sensor is determined to be caused by the panning operation or the like. The correcting lens is returned to the center of the movable range (a reference position that has a no displacement) and stopped.
In this connection, the shake detection signal may not be 0 exactly, but asymptotically close to 0 due to a residue signal or the like of a high-pass filter (HPF) or an integrator of a detection signal processing system when some rapid changes of the angle velocity signal occur at the end of the panning operation or the like. Therefore, when the image shake correction is resumed, the correcting lens is moved significantly by the shake detection signal to cause the swing-back of the image. To solve the problem, Japanese Patent Laid-Open No. 2006-113264 discloses a device for correcting the image shake by gradually changing a cut-off frequency for a signal processing based filter of the angular velocity at the end of the panning operation or the like. Also, Japanese Patent Laid-Open No. 2011-118073 discloses a method for performing driving of the correcting lens by speed control depends on the angular velocity without using the HPF or a LPF (integrator) having a significantly lower cut-off frequency in the signal processing based filter of the angular velocity that results in the swing-back. Also, Japanese Patent Laid-Open No. 2010-004370 discloses a device for correcting a shake by the correcting lens based on a shake signal detected by the angular velocity sensor and correcting the shake by the electronic image shake correction based on the shake signal of the low-frequency components. Thereby, the device can ensure a sufficient drive range of the correcting lens with respect to the large shake due to the panning operation or the like.
However, the technique described in Japanese Patent Laid-Open No. 2006-113264 has a weak effect on the image shake correction immediately after the panning operation or the like. Also, in the technique described in Japanese Patent Laid-Open No. 2011-118073, because the operation in which the position of the correcting lens is centered by position control, when exposure is not being performed, the effect of the image shake correction on the low-pass components of the shake detection signal such as a swing of the user's body is weakened. Also, if the offsets of the angular velocity sensor and the temperature fluctuation are large, and the shake at a low-frequency is relatively large during photographing while walking or the like, the position of the correcting lens deviates from the center of the movable range since this technique does not use the HPF. If a crystal gyro sensor or the like with a small offset and the temperature fluctuation is used, the cost may increase. Also, the technique described in Japanese Patent Laid-Open No. 2010-004370 reduces the performance of the image shake correction for the low-frequency during the exposure if the electronic image shake correction cannot be performed.